巨大な膜のパッチでマイクロ秒解像度で探査されたNa,Kポンプのチャネルのような機能

D W Hilgemann¹

¹Department of Physiology, University of Texas Southwestern Medical Center, Dallas 75235.

Science (New York, N.Y.)

|March 11, 1994

まとめ

ナトリウム・カリウム (Na,K) ポンプは,細胞外ナトリウム結合の際に超高速の電荷運動を通じて電流を生成します. マイクロ秒以内に発生するこれらの動きは,ポンプにとって不可欠です.

科学分野:

バイオフィジックス生物物理学
細胞生理学細胞生理学
イオン輸送機構イオン輸送機構

背景:

イオントランスポーターは,イオンチャネルと同様の機能で,イオンが膜を横断する動きを容易にします.
ナトリウム・カリウム (Na,K) ポンプのようなトランスポーターの電生成性は,細胞機能にとって極めて重要です.
イオン結合と電荷の移動の正確なメカニズムを理解することは,トランスポーター機能の解明の鍵です.

研究の目的:

ナトリウム・カリウム (Na,K) ポンプの電気生成特性について調べる.
細胞外ナトリウム結合に関連する電荷運動の運動学と条件を特徴づける.
細胞外イオン結合がNa,Kポンプの全体的な電気性に対する貢献度を測定する.

主な方法:

電気生理学的測定のために巨大な心臓膜パッチを使用しました.
特殊な技術を用いて超高速電荷の動きを測定した.
オアバインと細胞外ナトリウム濃度が電荷の移動に及ぼす影響を調査した.

主要な成果:

細胞外ナトリウムがNa,Kポンプと結合する際に,超高速充電運動 (4マイクロ秒以内) が観察されました.
これらの電荷の移動は,結合部位が細胞外側に向いている場合にのみ発生することを実証した.
充電運動は,オアバインと細胞外ナトリウムがないことによって廃止されていることが確認されました.

結論:

細胞外ナトリウム結合は,Na,Kポンプの急速な充電運動と直接関連しています.
これらの超高速の電荷移動は,ポンプの電気性の主要な,潜在的に排他的な源です.
この発見は,Na,Kポンプの機能とイオン輸送の分子機構に関する重要な洞察を提供します.

さらに関連する動画

11:55

Membrane Transport Processes Analyzed by a Highly Parallel Nanopore Chip System at Single Protein Resolution

Published on: August 16, 2016

08:33

Measuring Nucleotide Binding to Intact, Functional Membrane Proteins in Real Time

Published on: March 11, 2021

関連する概念動画

01:19

Ion Channels

The movement of ions like sodium, potassium, and calcium into and out of the cell is essential to maintain the electrochemical gradient in living cells. The ion channels—a class of membrane transport proteins—help maintain this ionic gradient for the smooth functioning of physiological activities such as maintaining cell size and volume, conducting nerve impulses, and gas and nutrient exchange.
Ion channels are specialized integral membrane proteins on the plasma membrane that allow specific...

01:30

Membrane Proteins

Plasma membranes have integral transmembrane proteins involved in facilitated transport. These proteins are collectively referred to as transport proteins, and they function as either channels for the material or as carriers themselves. Channel proteins have hydrophilic domains exposed to the intracellular and extracellular fluids and a hydrophilic channel through their core that provides a hydrated opening for solutes to pass through the membrane layers. Passage through the channel allows...

01:24

Non-gated Ion Channels

Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.

01:18

Patch Clamp

Many fundamental cell functions such as muscle contraction and nerve transmission rely on the electrical signals produced by the movement of positively and negatively charged ions across the cell membrane. One competent method to record current flowing across the whole cell or single ion channel is the patch-clamp technique.
In this method, a glass micropipette containing electrolyte solution is tightly sealed against a small portion of the cell membrane. As a result, a patch of the cell...

01:21

G-Protein Gated Ion Channels

GPCRs are primarily responsible for our sense of smell, taste, and vision. The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
Sensory organs,...